Ganged single axis solar tracker and its drive system

ABSTRACT

The present invention involves a ganged single axis solar tracker and its drive system having at least two rows of solar trackers and a drive mechanism. Each tracker row shares one common rotation axis and the at least two tracker rows are placed in parallel. At least one torque arm is rigidly and perpendicularly connected to the each tracker rotation axis. The drive mechanism has at least one rotary actuator, such as a slew drive, whose rotation axis is parallel to the tracker rotation axes. At least one drive torque arm is rigidly and perpendicularly connected to the drive rotation axis. The drive torque arm and the tracker torque arms are hinge connected with a series of rigid beams. The linkage beams are perpendicular to the tracker and drive rotation axes. The rotary drive rotates and creates a rotation movement. The drive torque arm follows the rotation movement of the drive, which consequently converts a linear push-pull movement in the linkage beams. The linkage beams push and pull the tracker torque arms, rocking the at least two rows of solar trackers to rotate about their axes and to follow the sun&#39;s movement.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to solar energy production and more particularlyto an apparatus for driving a number of rows of solar receivers tofollow the motion of the sun relative to the earth.

2. Description of the Related Art

Solar energy has gradually become an important alternative powerresource to help achieve the goal of sustainable development. Solarpower has a few unique advantages such as it is clean, abundant, and itproduces when the consumption is high. The biggest challenge the solarenergy is currently facing is its relatively high cost. Solar trackingsystems can improve incident angles of solar receivers such as solarthermal or photovoltaic modules (PV). These tracking devices have beensuccessfully used to improve power production efficiency, and thus toreduce solar power generation costs.

The prior art single axis trackers typically have one motor/drive pertracker row, thus limiting the total area of solar receivers driven byeach motor/drive. Solar tracker array using this technology will havehigh costs due to generally increased material usage, field constructionwork, as well as maintenance requirements. In order to reduce costsassociated with tracking, U.S. Pat. No. 6,058,930, to Shingleton,described a ganged single axis solar tracker system. In this system,multiple solar trackers are linked together with a linear motion linkageand operated by a single linear actuator, such as a hydraulic or screwjack, attached to a separate foundation located away from the solartracker array. The advantage of such a system is clear since the costsof motor and drive system have been shared by multiple tracker rows,thus the tracking costs per PV module have been substantially reduced.The system has also limitations. Firstly, the first linkage member closeto the drive has to withstand wind loads on the entire tracker array,thus it becomes less economy when the tracker array increases in size.Secondly, the linear actuator produces large up and down forces onto thefoundations and tracker beams near the drive, increasing costs for theseaffected members. Thirdly, the drive has to be located away from thetracker array, thus requiring extra land.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, a ganged singleaxis solar tracker array has at least two rows of solar trackers and adrive mechanism. The said solar trackers have rotation axes; solarreceivers are mounted onto the tracker rotation axes. Solar trackers inone row are rotatorily mounted onto at least one foundation and shareone common rotation axis. The at least two tracker rows are placed inparallel. At least one torque arm is rigidly and perpendicularlyconnected to the each tracker rotation axis. The rotation center of thetorque arm is coincident with the tracker rotation axis onto which thetorque arm is affixed. The driver mechanism has at least one rotaryactuator, such as a slew drive, whose rotation axis is parallel to thetracker rotation axes. At least one drive torque arm is rigidly andperpendicularly connected to the drive rotation axis. The rotationcenter of the drive torque arm is coincident with the drive rotationaxis. The drive torque arm and the tracker torque arms are hinge linkedwith a series of rigid beams. The linkage beams are perpendicular to thetracker and drive rotation axes. The rotary drive rotates to create arotation movement. The drive torque arm follows the rotation movement ofthe drive, which consequently converts a linear push-pull movement inthe linkage beams. The linkage beams push and pull the tracker torquearms, rocking the tracker rows to rotate about their axes and to followthe sun's movement.

The rotation centers of the two torque arms on any two adjacent trackerrows, and the two connecting joints between the two torque arms and thelinkage beam, form the four corner points of a quadrilateral. Similarly,the rotation center of the drive torque arm, the rotation center of anadjacent torque arm, and the two connecting joints between the twotorque arms and the linkage beam, form the four corner points of aquadrilateral.

In one embodiment, a ganged single axis solar tracker system has atleast two rows of solar trackers and a drive mechanism. The solartrackers have rotation axes; solar receivers are mounted onto thetracker rotation axes. Solar trackers in one row are rotationallymounted on at least one foundation and share one common rotation axis.At least two tracker rows are placed in parallel. At least one torquearm is rigidly and perpendicularly connected to the each trackerrotation axis. The rotation center of the torque arm is coincident withthe tracker rotation axis onto which the torque arm is affixed.

In one embodiment, the drive mechanism has at least one rotary actuatorwhose rotation axis is parallel to the tracker rotation axes. The rotaryactuator may be a slew drive, a worm gear, a planetary gear, or a slewring. At least one drive torque arm is rigidly and perpendicularlyconnected to the drive rotation axis. The rotation center of the drivetorque arm is coincident with the drive rotation axis. The drive torquearm and the tracker torque arms are hinge connected with a series ofrigid beams. The linkage beams are perpendicular to the tracker anddrive rotation axes.

In one embodiment, the rotation axis of the rotary actuator may becoincident with the rotation axis of one tracker row within the trackerarray, and may also be parallel to and away from the rotation axis ofany tracker row of the tracker array. The rotation axis of the rotaryactuator may further be located within or outside of the tracker array,and may be flat, tilted to the ground, or vertical.

In one embodiment, the tracker rotation beam may be of round or squarecross section, or truss. The ganged single axis solar tracker drivemechanism links and drives at least two rows of solar trackers. Thesolar trackers have rotation axes; solar receivers are mounted onto thetracker rotation axes. Solar trackers in one row are rotatorily mountedonto at least one foundation and share one common rotation axis. Atleast two tracker rows are placed in parallel. The single axis solartracker drive mechanism comprises of multiple torque arms which areperpendicularly and rigidly connected to the said each tracker rotationaxis. The rotation center of each torque arm is the tracker rotationaxis onto which the said each torque arm is affixed.

One embodiment of the single axis solar tracker drive mechanism furthercomprises of at least one rotary actuator or drive. The rotary drive hasone rotation axis which is parallel to the said tracker rotation axes.At least one drive torque arm is rigidly and perpendicularly connectedto the said drive rotation axis. The rotation center of the drive torquearm is coincident with the drive rotation axis. The said at least onedrive torque arm and the tracker torque arms are hinge connected with aseries of rigid beams. The linkage beams are perpendicular to thetracker and drive rotation axes.

In an exemplary embodiment, the rotary drive shares the rotation axis ofa tracker row, which can be a center row, a side row, or any other rowwithin the tracker array.

In another embodiment, the rotary drive has its rotation axis apart fromany tracker rows. The drive axis can be located near the center of, inbetween any two adjacent tracker rows within, or on one side and awayfrom, the tracker array.

The rotary drive includes but is not limited to slew drive, worm gear,planetary gear, or slew ring. The tracker and drive rotation axes arehorizontal, tilted, or vertical to the earth. The tracker rotation beamsvary by shapes, including but are not limited to round, square, and soforth. Apparently to those skilled in the art, the rotation beams may becomposed of truss, tubular or any composite of these members. The solarreceivers include but are not limited to flat panels, flat or parabolicreflectors/mirrors for the use of solar photovoltaic, thermal orconcentrator.

In another aspect of the present invention, a drive mechanism isemployed to drive at least two rows of solar trackers. Trackers haverotation beams onto which solar panels are affixed. Trackers in one rowshare one common rotation axis which are rotationally mounted on atleast one foundation and the at least two tracker rows are placed inparallel. The drive mechanism comprises of: at least one torque armwhich is rigidly and perpendicularly connected to the each trackerrotation axis, and the rotation center of the torque arm is coincidentwith the tracker rotation axis onto which the torque arm is affixed; atleast one rotary actuator, such as a slew drive, whose rotation axis isparallel to the tracker rotation axes; at least one drive torque armwhich is rigidly and perpendicularly connected to the drive rotationaxis, and the rotation center of the drive torque arm is coincident withthe drive rotation axis. The at least one drive torque arm and thetracker torque arms are hinge connected with a series of rigid beams.The said linkage beams are perpendicular to the tracker and driverotation axes.

The ganged single axis tracker and its drive mechanism has the followingadvantages: firstly, solar trackers can be conveniently placed in amirror layout about the rotary drive axis, and the maximum force enduredby the linkage member equals only to the forces from half of the entiresolar array. In another words, the linkage member with the same size inthe present invention can drive twice as many solar panels as per theprior art. Secondly, the drive system in embodiments of the presentinvention distributes wind forces in more appropriate manners since itproduces no additional uplift and down forces on nearby foundations andbeams, nor large compression force in the drive unit which could lead tobuckling failure in the screw jack as in the prior art. Thirdly, thedrive can share the tracker axis or be located within the tracker arraysuch that no additional land is required.

The above and many other objects, features, and advantages of thisinvention will be set forth in part in the detailed description tofollow, taken in conjunction with the accompanying drawings, and in partwill become apparent to those skilled in the art upon examination of thefollowing, or may be learned by practice of the claimed invention. Theobjects and advantages of the claimed invention may be realized andattained by means of the instrumentalities and combinations particularlypointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features and objects of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of an embodiment of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 illustrates a plan view of the prior art which employs a linearactuator to drive multiple single axis tracker rows.

FIG. 2 illustrates an east-west side view of the prior art which employsa linear actuator to drive multiple single axis tracker rows (or Section2-2 in FIG. 1).

FIG. 3 illustrates a plan view of an embodiment of the currentinvention, in which the drive axis coincident with one tracker axis nearthe center of the tracker array.

FIG. 4 illustrates an east-west side view of an embodiment of thecurrent invention, in which the drive axis coincident with one trackeraxis near the center of the tracker array (or Section 4-4 in FIG. 3).

FIG. 5 illustrates a north-south side view of an embodiment of thecurrent invention, in which the drive axis coincident with one trackeraxis near the center of the tracker array (or Section 5-5 in FIG. 3).

FIG. 6 illustrates a plan view of the second embodiment of the currentinvention, in which the drive axis coincident with one tracker axislocated at the end of the tracker array.

FIG. 7 illustrates a plan view of the third embodiment of the currentinvention, in which the drive axis is in-between and away from twoadjacent tracker rotation axes within the tracker array.

FIG. 8 illustrates a plan view of the fourth embodiment of the currentinvention, in which the drive axis is on one side of and away from thetracker array.

Corresponding reference characters indicate corresponding partsthroughout the several views. Although the drawings representembodiments of the present invention, the drawings are not necessarilyto scale and certain features may be exaggerated in order to betterillustrate and explain the present invention. The exemplification setout herein illustrates an embodiment of the invention, in one form, andsuch exemplifications are not to be construed as limiting the scope ofthe invention in any manner.

DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

The embodiments disclosed below are not intended to be exhaustive orlimit the invention to the precise form disclosed in the followingdetailed description. While the invention is subject to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and will herein bedescribed in detail. The invention should be understood to not belimited to the particular forms disclosed, but on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention. Rather, theembodiment is chosen and described so that others skilled in the art mayutilize its teachings.

With reference to the Drawings, and initially to FIGS. 1 and 2, a gangedsingle axis solar tracker array according to the prior art is shown.Multiple torque tubes in a row share a north-south axis 12, and a numberof solar receivers 10 are attached onto the tubes. At least two rows oftrackers are placed in parallel and apart from each other to form atracker array from east to west. Each tracker row 12 is rotationallymounted on at least one foundation 18, which is supported on the ground16. A torque arm 17 is rigidly and perpendicularly connected to each ofthe tracker rotation axis 12. The drive system according to the priorart comprises of a linear actuator 13 such as a hydraulic or screw jackwhich is supported on a foundation 11 above the ground 16, and a seriesof rigid linkage beams 14 and 15 which connect the torque arms 17. Alinear movement such as retraction or extension in the linear actuator13 produces a push or pull movement in the linkage beams 14 and 15; thelinkage beams push or pull the torque arms 17, which in turn create arotation movement of each solar tracker row about their axis 12. Thesolar tracker and its drive system according to the prior art has thefollowing characteristics: (1) the drive is a linear actuator; (2) thelinear actuator is located on one side of and away from the solartracker array (in this example, it is shown on the west; it can be onthe east side as well); the linear actuator and its foundation useadditional land on top of the land occupied by the solar array; (3) thefirst linkage beam 14 has to take the wind forces transferred from allsolar receivers except the first row from the drive. When the number ofrows of the tracker array increases, the load that the first linkagebeam 14 has to bear is high; (4) the linear actuator 13 and linkagebeams 14 and 15 are subject to compression forces, which could lead tobuckling damages within these parts; thus the size of the tracker arrayis substantially limited; and (5) the rotation center of the linearactuator, the rotation center of the first torque arm 17, and theconnection point of the first linkage beam 14 and the first torque arm17, form the three corner points of a triangle.

An embodiment of this invention is shown in FIGS. 3 to 5, which show asolar tracker array and its drive system, in its plan view (FIG. 3),east-west view (FIG. 4) and north-south view (FIG. 5), respectively. Thesolar tracker array comprises of multiple rows of solar trackers placedin parallel and aligned in north-south orientation, and its drivemechanism which rocks the solar trackers to follow the sun's east-westmovement. Trackers in one row share the same rotation axis 112 ontowhich solar receivers 110 are mounted. Each tracker row is rotationallymounted on at least one foundation 118, which is supported on the ground116. In each tracker row, a torque arm 117 is rigidly andperpendicularly connected to its rotation axis 112. The rotation centerof the torque arm 117 is coincident with the tracker rotation axis 112onto which the torque arm is affixed. The drive system of the trackerarray comprises of a rotary actuator or drive such as a slew drive 111.The drive is mounted on a drive foundation 119 which is affixed to theground 116. In general, a motor (as well as a controller) 120 ismechanically connected with the drive. The rotary drive has a rotationaxis or drive axis and a drive torque arm 113 is rigidly andperpendicularly connected to the drive axis. The rotation center of thedrive torque arm 113 is coincident with the drive rotation axis. Therotary drive is placed near the center of the solar tracker array, andit rotation axis is coincident with one tracker rotation axis. The drivetorque arm is hinge connected with other torque arms 117 thru a seriesof rigid beams 114 and 115. The rigid linkage beams 114 and 115 areperpendicular to the tracker axes. The two connection points between anytwo adjacent torque arms 113 or 117 and the linkage beam 114 or 115, andthe rotation centers of the two torque arms 113 or 117, form the fourcorner points of a quadrilateral. A rotary movement within the drive 111rocks the center tracker row and the drive torque arm 113 rotates aboutthe rotation axis 112. The rotary movement of the drive torque armconverts to a linear push-pull movement within the linkage beams 114 and115. The linkage beams push or pull the torque arms 117 to rock the eachtracker row to rotate about the each tracker rotation axis 112.Generally, the rigid linkage members are articulated to one another andto the torque arms of the respective rows of solar trackers, thusallowing the solar trackers to be employed on uneven terrain.

The solar tracker array and its drive system according to this inventionas shown in FIGS. 3 to 5 has the following characteristics: (1) thedrive is rotary actuator, such as a slew drive; (2) the drive axisshares one tracker rotation axis near the center of the tracker array;no additional land is needed for the drive and its foundation; (3) thelargest force the first linkage beam 114 has to take is equal to theforces on the east or west half of the tracker array instead of thatfrom the entire tracker array; (4) the drive and the drive torque arm donot bear large compression forces; and (5) The rotation center of thedrive or the drive torque arm, the two connection points of the firstlinkage member 114 between the drive torque arm and the first trackertorque arm, and the rotation center of the first tracker torque arm,form the four corner points of a quadrilateral.

In the first example, the rotary is a slew drive. In this and otherapplications, the rotary actuator or drive can also be slewing ring,planetary or worm gear. The optimal drive can be determined based oneconomy and site conditions. The use of various rotary drive typesshould be covered by the present invention.

In the first embodiment, the drive axis shares the rotation axis of thecenter tracker. Apparently, the drive axis can conveniently becoincident with any other tracker rotation axis within the trackerarray. In accordance with such an aspect of the present invention, thesecond embodiment of this invention is shown in FIG. 6. The differencebetween the second and first embodiment lies in that the drive axis inthe second embodiment shares the end tracker rotation axis.

The third embodiment of this invention is shown in FIG. 7. In thisexample, the drive axis is located near the center of the tracker arraywhile it is apart from any tracker rotation axis.

In the fourth embodiment of this invention as shown in FIG. 8, the driveaxis is located on one side of and apart from the tracker array.

In any particular applications of the present invention, solar receiverscan all have the same or various initial tracker angles; the trackerrotation beam can be of round or square cross section, a truss or anyother composite structure.

In all embodiments as shown the tracker axes are flat. It is notdifficult to persons skilled in the art that the tracker axes can bealigned tilted to the ground or vertical.

The term “ground” as used in reference to the foundation is not limitedto earth or soils, but can be a rooftop or any other supportingstructures.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains.

What is claimed is:
 1. A ganged single axis solar tracker systemcomprising at least two rows of solar trackers and a drive mechanism,said solar trackers have rotation axes and solar receivers; said solarreceivers being mounted onto the tracker rotation axes, said solartrackers in one row being rotationally mounted on at least onefoundation and share one common rotation axis, at least two tracker rowsbeing placed in parallel with at least one torque arm being rigidly andperpendicularly connected to the each tracker rotation axis, a rotationcenter of the torque arm being coincident with the tracker rotation axisonto which the torque arm is affixed; said drive mechanism having atleast one rotary actuator whose rotation axis is parallel to the trackerrotation axes, wherein said at least one drive torque arm is rigidly andperpendicularly connected to the drive rotation axis, the rotationcenter of the torque arm being coincident with the drive rotation axis,wherein the drive torque arm and the tracker torque arms are hingeconnected with a series of rigid beams having linkage beams that areperpendicular to the tracker and drive rotation axes.
 2. A ganged singleaxis solar tracker system according to claim 1 wherein said rotaryactuator is a slew drive, a worm gear, a planetary gear, or a slew ring.3. A ganged single axis solar tracker system according to claim 1wherein said rotation axis of the rotary actuator is coincident with therotation axis of one tracker row within the tracker array.
 4. A gangedsingle axis solar tracker system according to claim 1 wherein saidrotation axis of the rotary actuator is parallel to and away from therotation axis of any tracker row of the tracker array.
 5. A gangedsingle axis solar tracker system according to claim 4 wherein saidrotation axis of the rotary actuator is located within or outside of thetracker array.
 6. A ganged single axis solar tracker system according toclaim 1 wherein said rotation axes of the rotary actuator and trackersare flat, tilted to the ground, or vertical.
 7. A ganged single axissolar tracker system according to claim 1 wherein said tracker rotationbeam is of round or square cross section, or truss.
 8. A ganged singleaxis solar tracker drive mechanism for linking and driving at least tworows of solar trackers, wherein the solar trackers have rotation axesand solar receivers that are mounted onto the tracker rotation axes, andwherein solar trackers in one row are rotatorily mounted onto at leastone foundation and share one common rotation axis with at least twotracker rows being placed in parallel, the single axis solar trackerdrive mechanism comprising: a plurality of torque arms which areperpendicularly and rigidly connected to each of the tracker rotationaxes, a rotation center of each torque arm being coincident with thetracker rotation axis onto which each torque arm is affixed, said singleaxis solar tracker drive mechanism further comprising of at least onerotary actuator drive having one rotation axis which is parallel to thetracker rotation axes, and at least one drive torque arm which isrigidly and perpendicularly connected to the drive rotation axis,wherein a rotation center of the drive torque arm is coincident with thedrive rotation axis, the at least one drive torque arm and the trackertorque arms being hinge connected with a series of rigid linkage beams,the linkage beams being perpendicular to the tracker and arranged todrive rotation axes.